Many markets are moving to mercury-free zinc air batteries for hearing aids. Although more environ­mentally friendly, the new battery technology is not a great friend to hearing aid performance. In a test of Rayovac brand batteries, the first generation of mercury-free were found to perform significantly worse than batteries with mercury. However, the newest mercury-free battery technology from this manufacturer comes closer to previous battery per­formance. It is recommended that this generation of mercury-free batteries be used for GN hearing instru­ments. These batteries have an expiration date of 2015 and later.

The graph below shows how the battery voltage drops over time as a high load is applied (the red curve shows the load current). The blue curve is the performance for Rayovac with mercury, the pink is their first generation mercury-free, and the green is their latest generation mercury free.

Did You Know?
In GN wireless hearing instruments, the exit from streaming due to low battery and the low battery warning prior to hearing instrument shutdown operate on different principles. This is due to different demands to the battery performance:

The low battery warning is triggered by a steady fall in voltage. When the averaged voltage drops below a nominal level for at least 30 seconds, the warning is triggered and will continue every 5 minutes until device shutdown.

The wireless exit is triggered by successive dips in voltage below a nominal level over a very short time period. When streaming, the wireless trans¬mission is characterized by power pulses. The battery must be able to withstand the resulting momentary dips in voltage.

Hi Everett, each type of hearing aid can only use the battery size that correlates with it. If you currently use a 312 battery that is the only size that will fit in and work with your hearing aid. If you’re using zinc air batteries (most hearing aids do) make sure you let them “breathe” for 2 minutes after taking the sticker off and before putting them in your hearing aids. That will ensure full battery life.

Why doesn’t the company stamp the battery size and polarity on the outside of the case. I’ve made two trips to the pharmacy to buy batteries for my 88 year old mother and still did not get the correct ones. Wouldn’t cost a penny more to mold the info onto the case.

Hi Joe, thank you for reaching out to ReSound. The polarity is printed on the battery door and should be visible once open, look for the + sign. Included in the user manual are detailed instructions on how to change the batteries, as well as a section for the clinician to write in battery size. If you have questions beyond these instructions or cannot find the user manual, please contact your mother’s hearing care profession and they should be able to provide you with everything you need.